Railroad boxcars generally have an opening on one or both sides which are covered by a single door or an auxiliary door and a main door that can be opened for loading and unloading and are closed in a locked and sealed condition during transportation. In the past decades, a number of different manufacturers have been involved in the manufacture of railroad cars and, thus, a variety of different classes of railroad boxcars are being utilized by various transportation companies.
While certain standards are set as requirements for the various classes of railroad cars, there appears to be no fixed standard for the exact size of the opening that is created in the boxcar. Thus, while the openings of different car manufacturers are fairly close, there are some variations of the size of the opening for each of the variety of sizes and types of railroad cars. Manufacturers of such railroad cars appear to purposely design the dimension of the opening such that only a door manufactured by them will fit the size of the opening. It will be appreciated that the life span of the railroad car is considerably longer than the life span of the door, which is subject to considerable abuse during use. Thus, these doors must be replaced periodically and the manufacturer thereby has the opportunity for the sale of its custom-fitted doors.
While adjustable doors have been proposed for railroad cars, the types of adjustment that have been made heretofore have been not entirely satisfactory because the adjustment is made in close proximity to the upper edge of the door when a height adjustment is made and, thus, weakens the structural rigidity of the joints at a location which is most critical or is made at the lower edge where all of the support structure is located.